As storage technologies advance, disk drives continue to become faster and cheaper. As costs come down, computing, storage, and networking systems incorporate greater numbers of disk drives to maximize storage space and performance. As the numbers of drives in a system increases, power budgets must be adjusted.
Current disk drives, such as hard disk drives and CD drives, rely on mechanically rotating disks for storage of information. During operation, the disks rotate at very high rates of speed. Upon power-up and initialization, 3-4 times more current can be required to accelerate the rotation of the disk—or “spin up” the disk. In systems containing many such disks, a large amount of power is required upon power-up and initialization to spin up the disks. However, this large amount of power is required only during the time that the disks are accelerating. Once brought up to speed, the disks require much less operational power.
In the past, power supply systems have been engineered to supply a large peak power to support disk spin-ups. This solution is uneconomical in terms of space, thermal margin, and cost, especially in lower cost systems including multiple disk drives.
Some new storage standards, such as the SATA II standard as described in the “Serial ATA II: Extensions to Serial ATA 1.0a” published by the Serial ATA Working Group, provide out of band (OOB) staggered drive spin-up support. New disk drive controllers and drives that conform to the standard cause disk drives to spin up at different times, thus reducing required peak power. This functionality, however, is provided only in the newest disk drives and chip sets.
It would be advantageous to be able to implement staggered drive spin-up in systems that utilize legacy disk drive controllers, in order to reduce peak power requirements and achieve the advantages of decreased space, improved thermal margin, and lower cost.